Global Warming - Atmospheric Composition

Most Global Warming reports make it sound like most of the atmosphere is made of carbon dioxide (CO2). In fact, it is only 0.03% (and seasonally variable).

Actually, water vapor (another Green House gas) is a larger percentage of the atmosphere (0 to 4%) and completely swamps the effect of CO2.

Atmospheric Composition | Biosphere - Carbon Dioxide - Water Vapor - Other Gases
Greenhouse gases | Ice Cores | Meteorites

Atmospheric Composition

This data is from Water vapor varies from 0% over deserts and locations with temperatures below freezing to 4% over oceans.

Water vapor, Carbon Dioxide, and Methane are known as "Green House" gases precisely because their percentages are variable. To be completely precise, all the gases in the atmosphere, and the dust (which also varies), contribute to the "Green House" effect.

Unfortunately, these numbers are quite misleading because the concentrations vary with altitude. Also, 8,000 feet in the mountains has different concentrations than 8,000 feet over the oceans. (This is particularly true of the 4 variable gases.) Unfortunately, I do not have sources with that data.

IR Absorption

All atmospheric gases obtain heat via conduction (think hot parking lot) and convection (hot air rises). However, Nitrogen, Oxygen, and Argon are transparent to IR.

On the other hand, Water vapor, Carbon Dioxide, and Methane all absorb IR radiation directly - another reason to consider these as Green House gases.


For the most part, the biosphere (all plants and animals, and the surface of the planet) is in equilibrium with the atmosphere.

Carbon Dioxide

Plants absorb Carbon Dioxide to make sugar and cellulose (polymerized sugar - sort of a natural plastic, aka "wood"). (Plants also make oils, amino acids, and many other carbon-base compounds. However, cellulose is the most common product.) Eventually, the plants die, decay, and return most of the Carbon Dioxide back to the atmosphere.

There are 3 notable exceptions to this balance

Thus, all the "fossil" fuels (coal and oil) were originally made from Carbon Dioxide found naturally in the atmosphere.

To a very minor extent, humans (mostly rich Americans) burn coal and oil which returns some Carbon Dioxide to the atmosphere ... but this is insignificant compared to what has been removed.

Water Vapor

Because of the large reservoir of liquid water (about 75% of the Earth's surface), the amount of water in the atmosphere (normally referred to as relative humidity) is controlled by local temperature.

From Hydrologic Cycle

Other Gases

The other 2 atmospheric gases (Nitrogen and Oxygen) are thought to be recycled with no loss of balance - except for the Oxygen used to make limestone.

One theory states that the Oxygen in the atmosphere was created when UV light (from the sun) split water into Hydrogen and Oxygen. Eventually, the light Hydrogen escaped into space and the Oxygen was left.

Another theory is that the original atmosphere was mostly Carbon Dioxide and that there was very little Oxygen. This theory states that single celled plants (algae and diatoms) processed the Carbon Dioxide and produced the current atmospheric Oxygen. The primary evidence for this is Banded Hematite - iron oxide rocks with alternating grey and red bands.

Actually, Banded Hematite only indicates that the early earth did not have as much Oxygen as there was a billion years later ... but it does not really favor one theory over the other.

Greenhouse gases

Though all atmospheric gases contribute to the Greenhouse effect, only 2 are significant to this argument.

There is a small amount of methane in the atmosphere, but


When an amount of methane is released to the atmosphere, half of it will be gone in some number of years - This is termed its atmospheric half-life.

References for this type of data are weak - I will add more when I find them.

In the atmosphere, methane (CH4) reacts with -OH radicals to create carbon dioxide (CO2) and water vapor (H2O). Typically, this reaction is fast enough to remove newly released methane in less than 10 years. (This implies a half-life of one to two years.) However, if the amount of methane significantly exceeds the number of OH radicals, then the reaction is limited by the rate of radical -OH creation. This is one of the trigger conditions where the normal feedback no longer works and a different mechanism is used. The last time this appears to have happened is about 55 million years ago - the global heating of the Late Paleocene Thermal Maximum (LPTM) lasted about 100,000 years. This is significant partly because the global warming was NOT associated with an increase in CO2. Methane Explosion Warmed the Prehistoric Earth, Possible Again

More on Water

Water both increases and decreases the Earth's temperature. However, which ever of these functions it is performing, it really is the main Greenhouse gas, and when present, it completely swamps the effect of CO2.

Ice Cores

The Greenhouse Effect, Greenhouse Gases, and Global Warming

This is an interesting paper showing Greenhouse gas concentrations for the last 200,000 years (based on Vostok ice cores). It also explains that CO2 is not the only Greenhouse gas. Unfortunately, I have not been able to find a current site with this chart (it was originally available on a NASA site) - this reference is from the WayBack Machine (nothing on the internet can ever be deleted).

Notice that the global temperature (center trace) is currently falling as CO2 (on the right) is still increasing. From the chart, it appears that methane actually controls the climate and that CO2 increases AFTER the temperature starts to rise. (This is most obvious at about 135,000 years BP.)

In fact, the paper states that the Earth would be 60F (33C) cooler if all Greenhouse gases were removed from the atmosphere.

Overall, this is one of the best written and easiest to understand papers I've seen explaining Global Warming and Greenhouse gases. It makes you wonder why it is no longer available.

Ice core data from around the world, including that from Vostok, Antarctica, is provided by NOAA.

The Wikipedia provides a 450,000 year graph of Ice Age Temperature changes based on Ice Cores and sediment cores (using foraminifera). From this, it is obvious that the average Earth temperature is about 12F cooler than it is today. It is also obvious that the next Ice Age is already late.

Filtered Data

There is an interesting problem with ice cores - the atmospheric gases in the cores were trapped several hundreds or thousands of years AFTER the snow fell. This is due to the nature of snow with spaces between the particles. As more snow falls, the extra weight compresses the pack until the spaces seal and the gases can no longer exchange with the atmosphere. Unfortunately, the amount of time for this to happen is highly variable ... from 30 years to about 7,000 years.
The gas age–ice age difference (age) is as great as 7 kyr in glacial ice from Vostok; it is as low as 30 yr in the rapidly accumulating Antarctic core DE 08.
Gases in ice cores, Colloquium Paper, Proceedings of the National Academy of Sciences of the United States of America, 1997 August 5
New research on the Vostok ice core indicates the age difference between air and ice may be ~6000 years during the coldest periods instead of ~4000 years, as previously assumed.
Historical carbon dioxide record from the Vostok ice core *

As a direct result, interpreting ice core data is iffy at best (but the popular press never mentions any of this).

Age of Greenland's ice sheet (Sept 01, 2004, USA Today) provides a good description of how snow becomes a glacier - notice that it says that the process takes 200 years or more.

Introduction to the Lithosphere says that it takes only about 100 years for snow to become glacial ice.

How is this important ... as long as the air between the snow crystals is connected to the atmosphere, they will both have the same concentrations of CO2, methane, and all the other gases. After a period of time, there will be enough additional snow (weight) that some of it will become ice and some of the gas will be trapped in bubbles inside the ice. After an additional amount of time (and more snow), 100% of the gas will be trapped in bubbles.

You might argue that scientists can just extract the air from a single bubble ... but it isn't that simple. With increased time and weight the bubbles compress and the gases become entrapped in clathrates. In order to remove the gases from these layers, the ice is crushed and heated thus mixing the gases that were originally captured in separate bubbles at separate times. As a result, the extracted gases provide a time averaged representation of past atmospheres.

For the Vostok ice core gas extraction and measurements ... involved crushing the ice sample (~40 g) ... without melting it, ... and analyzing the CO2 concentrations by gas chromatography
Historical carbon dioxide record from the Vostok ice core *
This filtering is similar to what you see with stock quotes Well, that is what the ice core data represents - 400,000 years of data smoothed with perhaps a 1,000 year moving average. (Of course, the public normally sees only a few hundred years of data.)

(I actually don't know what value should be assigned to the moving average ... but I do know that this natural filter removes the peaks, and I also know that the public is shown these charts without the natural filter being mentioned.)


Dr. Singer says that the Vostok ice cores show that the last ice age ended about 600 years BEFORE the observed increase in CO2.

Prof. Zbigniew Jaworowski testified before the US senate - he claims that the ice core data has been faked (dates modified and averages manipulated) to fit the Global Warming theory. In fact, he claims that during several periods when the Earth was much cooler than today, the atmospheric CO2 concentration was significantly higher.

In 2007, Dr. Hansen published a paper admitting that the Vostok ice core indicates that the CO2 values changed after the temperature. But ... he has a solution - Just change the data. The argument goes like this.

Perhaps it would make more sense to change the theory. To be clear, Dr. Hansen proves, beyond a reasonable doubt, that increasing CO2 will NOT have any effect on temperature.

Meteorites Cause Global Warming

This is a radical alternate theory that makes a lot of sense. (As far as I know, it is original with me ... therefore, it must be wrong.)

It is interesting that I can not find a single reference that documents how much the mass of the atmosphere changes from year to year.

It is well known that the amount of gas (number of molecules) in the atmosphere increases when gas dissolved inside the molten part of the Earth is released (usually through volcanism).

It is also well known that gas escapes the planet from the top of the atmosphere. (It is believed that, even though Mars once had liquid water and an atmosphere, it currently has almost no atmosphere - it just escaped into space. Presumably, most of it came to Earth - but there is no way to know for sure.)

This mass balance may be the most important feedback system in maintaining the current relatively warm planet. As the planet warms, more water enters the atmosphere. This in turn causes the planet to retain more solar radiation ... and the planet gets even warmer. Unchecked, this positive feedback system would overheat everything.

The check is that hotter gases are more likely to escape into space (because they have more energy). With less atmosphere, less heat is retained and (if we are lucky) the temperature becomes stable.

Using this theory, eventually enough gas will escape into space that the Earth will start to cool off. The water will fall out of the atmosphere, the ice caps will begin to grow, and the Earth will cool off rapidly (because of the loss of water vapor - the major Green House gas). This will continue until a large rock (meteorite) cracks the crust, another large quantity of gas is released, and the Earth is able to capture more heat than it is loosing.

Notice that the volume of the atmosphere is not really the important parameter (mainly because this changes with temperature and because a fixed number of molecules is thought block the radiation of heat regardless of their temperature, pressure, or volume ... I do not know if this experiment has been done). However, if more molecules are added, more heat will be retained.

There are several other items that affect the mass of the atmosphere

So the obvious conclusion is that, without very large meteorites (asteroid collisions), the Earth will eventually cool off and become uninhabitable. (Of course, this will take billions of years :) so it's not really relevant to the Global Warming arguments. On the other hand, it is one possible argument to explain the Ice Ages.)

Additional notes

In many parts of the world, oil seeps out of the ground ... causing natural pollution. Associated with these seeps is the release of natural gas (70-90% methane). A well placed, relatively small asteroid could easily affect the rate that these near surface gases enter the atmosphere. Since ice core data indicates that there is a sudden increase in methane before the end of an ice age, and because that same data indicates that methane is the only really important greenhouse gas, the ice core data actually supports the "asteroid ends the ice ages" theory.

The "fact" (I can't prove it) that methane's half life in the atmosphere is less than 10 years indicates that something very major causes the spikes.

Additional References:

More Evidence For and Against Meteorites

This 450,000 year graph of Ice Age Temperature changes shows that each Ice Age ended with a real sharp temperature spike. In addition, these spikes are separated by somewhat random periods.

My interpretation of this graph is that something catastrophic happened, the Earth got hotter, then it got cooler, until the next rock hit. Some of the smaller spikes would indicate smaller meteorites.

There are, of course, several other possible explanations - change in the brightness of the sun, dust in space, and the like. But the sudden increase followed by a slow decrease, and the irregular period, are more likely caused by collisions.

The strongest evidence against the asteroid theory is a lack of dust in the ice cores. Every time a large volcano erupts, it adds a layer of dust in the ice cores - these are thin ... but easily visible. If either an asteroid or a volcano caused the end of an ice age, then there should be a layer of dust at that point in the cores. Since the dust is missing, then the asteroid theory is probably wrong. But what if the asteroid hit in the middle of the ocean ... or if a small asteroid hit in an oil seep?

Of course it is also possible that something as simple as an earthquake changed the amount of methane released. After all, La Brea is in Los Angeles and near the San Andreas Fault ... several other major seeps are also in active regions.

Author: Robert Clemenzi
URL: http:// / Global_Warming / Atmospheric_Composition.html